The present invention relates generally to the cooling of heat-generating devices, and more particularly, to an apparatus and a method for cling multiple chips using fluid.
The demand for compact, high speed, and multi-functional semiconductor devices or chips, as they are commonly known, is ever increasing. As these chips are shrinking in size and performing many tasks at high speeds, during operation extremely high amounts of heat are usually generated. To keep these chips operational and durable, the heat must be efficiently extracted to lower the temperature of the chips to a required level. A conventional cooling technique involves mounting a heat dissipating material, such as a heat sink, onto the surfaces of the chips to dissipate the heat. Another cooling technique requires mounting the chips on a printed circuit board (PCB), and running coolant over the exposed surfaces of the chips. Yet another cooling technique requires mounting the chips on a PCB over through-holes in the PCB. Coolant is then fed over the bottom surfaces of the chips via the though-holes. The disadvantage of these techniques is that only one surface or a partial surface of the chips is in contact with the coolant, therefore limiting the amount of heat removed from the chips.
Other more advanced conventional cooling techniques are described in U.S. Pat. Nos. 5,380,956, 4,879,629, 5,978,220, and 5,901,037.
In U.S. Pat. No. 5,380,956, a multi-chip cooling method is proposed. Chips are mounted on a plurality of substrates in such a manner that portions of the top and bottom surfaces of the chips are exposed. The substrates are arranged inside a module so that when coolant flows through the module, the coolant is in contact with the exposed portions of the top and bottom surfaces of the chips, thereby extracting heat from the chips. A limitation of this technique lies in the sequential and serial flow of the coolant over the different chips mounted on the different substrates. This means that the chips mounted on the substrates arranged downstream of the flow path of the coolant are not effectively cooled. This is because by the time the coolant reaches these chips, the coolant having extracted and retained heat generated by the chips upstream is not therefore capable of effectively cooling these chips. A further limitation lies in the way the chips are mounted on the substrates. Significant portions of the surfaces of the chips are used for adhering the chips to the substrate. Thus, it is not possible to expose the entire surface of the chips to the coolant.
U.S. Pat. No. 4,879,629 describes a method for concurrently cooling a plurality of integrated circuit chips mounted on a substrate. This is achieved by passing coolant through channels formed between the elongated fins of a plurality of heat sinks. The plurality of heat sinks are attached to a plurality of heat-conducting studs that are attached to the plurality of integrated circuit chips for receiving heat generated by the integrated circuit chips.
In U.S. Pat. No. 5,978,220, chips are mounted on a substrate and the substrate is coupled to a cold plate. The cold plate is kept cool by flowing coolant thereonto, thereby indirectly cooling the chips.
In U.S. Pat. No. 5,901,037, elongated micro channels are formed in a substrate that carries one or more transistor dies. Coolant is fed through the micro channels for extracting the heat from the dies.
In the foregoing conventional cooling techniques, the coolant either does not cool the heat-generating devices directly but through intermediate materials or extracts heat only from a portion of the surface of the heat generating devices. Thus, the cooling of the devices is restricted to the amount of heat the intermediate materials can dissipate or the amount of heat the coolant is capable of extracting, respectively. Therefore, the amount of heat removed using the conventional methods is limited.
From the foregoing description, it is apparent that there is a need for a way to adequately dissipate heat from the surface of the heat-generating devices in the limited physical space that is available.
In accordance with a first aspect of the invention, there is provided a method for fluid-based cooling of heat-generating devices, the method comprising the steps of:
mounting a heat-generating device onto a first portion of the surface of a first carrier;
spatially displacing the heat-generating device from the first portion of the surface of the first carrier for forming a first channel therebetween;
stacking a second carrier and the first carrier;
spatially displacing the second carrier from the first carrier for forming a second channel between a portion of the surface of the first heat-generating device and a portion of the surface of the second carrier;
enclosing at least a portion of the second carrier, the heat-generating device and at least a portion of the first carrier; and
introducing cooling fluid into the enclosure and into at least one of the first and second channels, the cooling fluid being substantially electrically non-conductive and for extracting heat from and thereby cooling at least one of the heat-generating device and at least one of the portions of the surface of the first carrier and the portion of the surface of the second carriers,
wherein heat generating devices are mountable only on each of the portion of the surface of the first carrier and a portion of the surface of the second carrier, the portion of the surface of the first carrier being substantially parallel to and facing the same direction as the portion of the surface of the second carrier.
In accordance with a second aspect of the invention, there is provided a cooling assembly for fluid-based cooling of heat-generating devices, the cooling assembly comprising:
a first carrier;
a heat-generating device mounted on a first portion of the surface of the first carrier;
a first channel formed by spatially displacing the heat-generating device from the first portion of the surface of the first carrier;
a second carrier, wherein the first and second carriers are stacked;
a second channel formed by spatially displacing the second carrier from the first carrier, the second channel being the space between a portion of the surface of the heat-generating device and a portion of the surface of the second carrier; and
an enclosure, for enclosing at least a portion of the second carrier, the heat-generating device and at least a portion of the first carrier,
whereby cooling fluid is introduced into the enclosure and into at least one of the first and second channels, the cooling fluid being substantially electrically non-conductive and being for extracting heat from and thereby cooling at least one of the heat-generating device and the at least the portions of the first and second carriers,
wherein heat generating devices are mountable only on each of the portion of the surface of the first carrier and a portion of the surface of the second carrier, the portion of the surface of the first carrier being substantially parallel to and facing the same direction as the portion of the surface of the second carrier.
In accordance with a third aspect of the invention there is disclosed a method for fluid-based cooling of heat-generating devices, comprising the steps of:
mounting a heat-generating device onto a first portion of the surface of a first carrier;
spatially displacing the heat-generating device from the first portion of the surface of the first carrier for forming a first channel therebetween the heat generating device being substantially received within a concavity, the concavity being formed in the first carrier and defining the first portion of the surface of the first carrier at least a portion of the first channel extending within the concavity;
stacking a second carrier and the first carrier;
spatially displacing the second carrier from the first carrier for forming second channel between a portion of the surface of the first heat-generating device and a portion of the surface of the second carrier;
enclosing at least a portion of the second carrier, the heat-generating device and at least a portion of the first carrier; and
introducing cooling fluid into the enclosure and into at least one of the first and second channels, the cooling fluid being substantially electrically non-conductive and for extracting heat from and thereby cooling at least one of the heat-generating device and at least one of the first portion of the surface of the first carrier and the portion of the surface of the second carrier, the concavity being shaped and dimensioned for the passage of the cooling fluid therethrough,
wherein heat generating devices are mountable only on each of the portion of the surface of the first carrier and a portion of the surface of the second carrier, the portion of the surface of the first carrier being substantially parallel to and facing the same direction as the portion of the surface of the second carrier.